1. Field of the Invention
This invention relates to data compression and playback.
2. Discussion of Prior Art
Related data sets may be closely linked such that it is desirable to play back both simultaneously. Several volumetric data sets measuring different physical parameters sampled at substantially the same locations can exist. For example, in meteorological data this may be wind velocity and temperature of a given volume.
This may also apply to several volumetric data sets acquired by a medical imaging device of the same volume of a subject. For example, in ultrasonic imaging, a Doppler shift data set in the detected ultrasonic frequency signal may be used to quantify blood speed and direction of flow in addition to the standard imaging data set.
In Magnetic Resonance Imaging, thermal and velocity data sets may be used in addition to the standard MR image data set, the additional information being played back in imaging by color coding on an otherwise gray-scale image. Color coded overlays have been used to show thermal hot-spots in phase-sensitive temperature imaging. Color coded overlays have also been used to highlight areas of activation in functional brain MRI scans.
One challenge with existing methods of playback is that the data set containing the additional information is sometimes as large (or larger) than the primary data set. This can greatly overload the disk capacity and data-transfer bandwidth of a scanner.
Playback of processed data is also difficult since much information may be lost during processing. For example, in MR imaging playback, it is frequently convenient to reduce a three-dimensional data set into a two-dimensional projection image. This is often done using a Maximum Intensity Projection (MIP). Current methods for the generation of MIP images from three-dimensional phase contrast angiograms are applied to the magnitude component of the data, thereby losing all directional information. MIP data from the quantitative velocity data could be performed, but the MIP would have to be performed three times (one for each flow component) over the three-dimensional data set to provide a full analysis.
Currently, there is a need for a system which incorporates additional information in primary data sets allowing display of more than one parameter simultaneously.